#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int Frog(int n)
{
	if (n == 1)
	{
		return 1;
	}
	else if (n == 2)
	{
		return 2;
	}
	else
	{
		return Frog(n - 1) + Frog(n - 2);
	}
}

int main()
{
	int n = 0;
	int ret = 0;
	scanf("%d", &n);
	ret = Frog(n);
	printf("%d", ret);
	return 0;
}

